The disclosure relates to a hydrostatic positive displacement machine.
DE 10 2010 054 416 A1 shows a positive displacement machine of the type in question which is configured as a vane pump. This has a housing, on which a rotor fitted with radially movable vanes is mounted so as to be rotatable about an axis of rotation. The vanes are supported on an inner circumferential surface of a cam ring mounted eccentrically with respect to the rotor. An annular space is formed between the rotor and the cam ring, said annular space being subdivided by the vanes into hydrostatic working spaces which can be brought alternately into pressure medium connection with a high-pressure and a low-pressure connection of the positive displacement machine.
On the circumference, the cam ring has two diametrically arranged outer circumferential surface segments, by means of which it is guided in translation transversely to the axis of rotation on inner surface segments of the housing in order to adjust a displacement volume of the vane pump.
When some of the working spaces are connected to high pressure, the inner circumferential surface of the cam ring is subjected to pressure medium, resulting in the deformation thereof. Accordingly, the outer circumferential surface segments are also deformed, leading to non-uniform distribution of the surface pressure between the outer circumferential surface segments and the inner surface segments. This results in increasing wear of the participating surface segments as the working pressure increases.
Various concepts for reducing wear are known from the prior art. A first is shown by the German Laid-Open Application mentioned. In this case, one or more groove profiles subjected to pressure medium are formed in one or more of the surface segments, thereby making it possible to produce a hydrostatic relief field by means of which friction between the surface segments is reduced.
This secondary measure for reducing wear by reducing friction proves disadvantageous since production of the grooves is expensive.
In an alternative concept to this, the cam ring is mounted in rolling or revolving contact by means of its outer circumferential surface segments on the inner surface segments of the housing.
The disadvantage of this is the high complexity of the apparatus, which makes the positive displacement machine expensive.